The present invention relates to the disposal of the cuttings from oil and gas well drilling, and more particularly to an improved method and apparatus for the disposal of cuttings generated during drilling of an oil and gas well. More particularly, the present invention relates to a method and apparatus for disposal of cuttings generated during the drilling of an oil and gas well using a barge wherein an improved configuration enhances the storage, transportation, and ultimate disposal of cuttings.
In the drilling of oil and gas wells, a drill bit is used to dig many thousands of feet into the earth's crust. Oil rigs typically employ a derrick that extends above the well drilling platform which can support joint after joint of drill pipe connected end to end during the drilling operation. As the drill bit is pushed farther and farther into the earth, additional pipe joints are added to the ever lengthening “string” or “drill string.” The drill pipe or drill string thus comprises a plurality of joints of pipe, each of which has an internal, longitudinally extending bore for carrying fluid drilling mud from the well drilling platform through the drill string and to a drill bit supported at the lower or distal end of the drill string.
Drilling mud lubricates the drill bit and carries away well cuttings generated by the drill bit as it digs deeper. The cuttings are carried in a return flow stream of drilling mud through the well annulus and back to the well drilling platform at the earth's surface. When the drilling mud reaches the surface, it is contaminated with small pieces of shale and rock which are known in the industry as well cuttings or drill cuttings.
Well cuttings have in the past been separated from the reusable drilling mud with commercially available separators that are know as “shale shakers.” Some shale shakers are designed to filter coarse material from the drilling mud while other shale shakers are designed to remove finer particles from the drilling mud. After separating well cuttings therefrom, the drilling mud is returned to a mud pit where it can be supplemented and/or treated prior to transmission back into the well bore via the drill string and drill bit to repeat the process.
The disposal of the separated shale and cuttings is a complex environmental problem. Drill cuttings contain not only the mud product which would contaminate the surrounding environment, but also can contain oil that is particularly hazardous to the environment, especially when drilling in a marine environment.
Traditional methods of cuttings disposal have been by individual storage tanks, dumping, bucket transport, cumbersome conveyor belts, and washing techniques that require large amounts of water. Adding water creates additional problems of added volume and bulk, messiness, and transport problems. Installing conveyors requires major modification to the rig area and involves many installation hours and very high cost.
In the Gulf of Mexico for example, there are hundreds of drilling platforms that drill for oil and gas by drilling into the subsea floor. These drilling platforms can be in many hundreds of feet of water. In such a marine environment, the water is typically crystal clear and filled with marine life that cannot tolerate the disposal of drill cuttings waste such as that containing a combination of shale, drilling mud, oil, and the like. Therefore, there is a need for a simple, yet workable solution to the problem of disposing of oil and gas well cuttings in an offshore marine environment and in other fragile environments where oil and gas well drilling occurs.
Open top barges are not approved by the Coast Guard for use in the Gulf of Mexico because of the risk of discharges into the environment.
Prior art tank systems have included tanks with hatch openings into which drill cuttings can be placed. These prior art tanks also have attachments for enabling lift lines to be affixed to the tank so that it can be transported to and from offshore platforms and emptied when full. Further examples of these tanks are shown in one or more of the following U.S. Pat. Nos. 5,971,084; 5,564,509; and 5,402,857, which are each incorporated herein by reference. Although these tanks address the risk of discharge of drill cuttings into the environment, the tanks suffer from the disadvantage that they must be individually filled and emptied. Additionally, the tanks must be loaded onto the transporting vessel before being filled with cuttings, transported to the disposal site, off loaded from the transported vessel, and then cuttings from each tank are unloaded individually. This is a time consuming and cost prohibitive process.
There is a need for a system which allows fast and economical transport and disposal of drill cuttings from a drilling rig.
While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.”